Left has the power of a triceratops combined with a single MP5 submachine gun which is terrifying, but adding in the 500ml bottle of Mug root beer, the second best commercially available root beer? Fearsome. I don't know what the fuck a Lavaclaw Reaches is, but all I know is it's not a Baneslayer Angel. The 360 has some punching power, but it's also just going to red ring as soon as it gets into the arena, and this is the only joke I could have made about it obviously. San Andreas? CJ armed with whatever that weird rod thing is? Pretty good. Oh, and I guess Jerry or whatever from the Witcher is there.
Left's Combat Score: 5000.
Right has UNSC Master Chief Petty Grade and Spartan Mk.2 John-117 who's free fallen from high orbit once and survived, so he's at least equal to the single MP5. The 5E beholder has an average of 180 hit points (19d10 plus 76 I believe off the top of my head accounting for level bonuses and con mod) while the triceratops has an average of only 95 (10d12 plus 30, I had to look that one up). The beholder has an average single target damage output of 12 with its bite followed by up to 3 random eye rays accounting for its legendary actions; assuming it gets only the weakest disintegration ray which does an average of 40 damage, that's a total of 40+40+40+12 = 132 average damage output per turn, capable of being spread around at other targets. The triceratops has an average of 22 (listed as 24 in the books stat block which is not correct?) from its gore attack plus an average of 21 (again, listed as 22 in the book which is not correct) if we count the follow-up stomp attack, total of 43. Not even accounting for AC and attack bonuses, that's a fucking dead triceratops in a single turn. I guess some other things are on rights team, but I got too distracted by DnD. I like the Genesis.
Right's Combat Score: why are you reading this?
Winner: I don't know.